Does foam insulation need vapor berrier?


Old 01-11-06, 03:20 PM
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Does foam insulation need vapor barrier?

I am planning to finish my semi -finished basement. Previous owner has done the framing around the walls with a layer of foam between frames and the wall as insulation. Should I add any vapor barrier before installing dry walls?

Last edited by Cyrus; 01-11-06 at 03:45 PM.
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Old 01-12-06, 02:57 AM
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It depends on whether or not the foam has a vapor barrier built in. You can tell by the thin layer of plastic adhered to the face. Again, depending on how tight the fit is between the studs, also. You would benefit by running a bead of non expanding foam along the edges and around the receptacles and switches in order to insure a good seal.
Old 01-14-06, 07:05 AM
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Sorry, I read it twice and still dont know what you mean by "between frames and the wall insulation"
Old 01-20-06, 08:44 PM
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I'm in the planning stage of finishing my basement and have done quite a bit of research regarding insulation. Of course you will find many different opinions. I will offer mine as and ME and having done a fair amount of research for what it's worth.

New data seems to indicate NOT having a vapor barrier when insulating basement walls. XPS or extruded polystryene foam is preferred becasue it is vapor permeable to some extent, allowing the wall to out gas (breath). In addition when applied directly to the concrete it prevents condensation of warm (wet) air against the colder concrete.

Now this may all be overkill as many people have successfully finished basements using other techniques but if you are looking at the long term, say 10 or more years then it may be worth it to consider the physics of the problem.

As I said there are lots of valid opinions on this topic.


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